Communication method between a badge and a motor vehicle

ABSTRACT

The invention concerns a communication method between a badge and a vehicle whereby a low range transmitter associated with the vehicle transmits a low frequency signal towards the badge which replies by sending a RF signal of longer range towards the vehicle. A receiver of the badge designed to receive a RF signal is placed in standby mode in accordance with a predetermined rhythm and a transmitter associated with the vehicle sends during a standby phase of the badge a RF signal whereto the badge replies with a RF signal. The invention is applicable to hands-free systems.

[0001] The present invention relates to a process of communicationbetween a badge and a motor vehicle provided with a hands-free system.

[0002] A hands-free system permits gaining access to a vehicle andstarting the latter without having to use a mechanical key. The user ofthe vehicle is thus simply provided with a badge which is in the form ofan electronic card. This badge is detected and recognized by a controland management device associated with antennas disposed onboard thevehicle. If the badge is identified by the control and management deviceas being a badge authorized for the vehicle, the bearer of the badge canenter the vehicle simply by grasping a door handle and start the motorof the vehicle by simple action on a button.

[0003] More generally, for such a hands-free system, a group of antennasis adapted to detect the presence of the badge outside the vehicle andanother inside the latter. These antennas are adapted to emit in thedirection of the badge an LF (Low Frequency) signal of a frequencytypically of the order of 125 kHz. These antennas have a short range,generally of the order of meters. It is thus possible, in a knownmanner, to locate a badge within or outside of the vehicle.

[0004] To locate a badge, a group of antennas, for example internalantennas, emit an LF signal. When a badge located within the vehiclereceives this signal, it responds by sending an RF (Radio Frequency)message typically of a frequency of 433 MHz.

[0005] Thus the badge is provided with an LF receiver, and an RFemitter, whilst the vehicle is provided with LF emitters and an RFreceiver. Only a single RF receiver is needed, because the range of theRF signal emitted by the badge is of the order of tens of meters and allthe vehicle can be covered.

[0006] The drawback of the communication process described above is thatthe LF emitting antennas within the vehicle do not always cover all theinside of the latter. Thus, as a function sometimes of the occupancy ofthe vehicle and given the short range of the LF signals, zones maskedfrom LF reception can exist within the occupant space. Thus, in spite ofthe presence of a badge within the vehicle, the latter not beingdetected, functions such as starting the vehicle can be frustrated. Thesystem described above can also locate a badge in the occupant space ofthe vehicle and not “see” a badge located in a masked region. Thevehicle could thus be conventionally lockable and unlockable despite thepresence of a badge within the vehicle. If the badge is visible from theoutside, a troublemaker could thus break in and take the badge and makeoff with the vehicle.

[0007] The present invention thus has for its object to provide aprocess for communication between the badge and the vehicle permittingreliably locating a badge within the latter.

[0008] To this end, the process provided is a process of communicationbetween a badge and a vehicle according to which a short range emitterassociated with the vehicle emits an LF type signal in the direction ofthe badge which responds by sending an RF type signal of longer range inthe direction of the vehicle. A short range signal can be consideredhere as a signal which does not cover all of the interior space of thevehicle whilst the longer range signal covers all the interior and allthe vehicle.

[0009] According to the invention a receiver of the badge adapted toreceive an RF type signal is placed on standby according to apredetermined rhythm and an emitter associated with the vehicle sends,during a standby phase of the badge, an RF type signal to which thebadge responds with an RF type signal.

[0010] In this way, the signal emitted by the vehicle to identify abadge is a long range signal and all the badges located within thevehicle receive this signal and are able to respond to it.

[0011] According to an example of embodiment of a process according tothe invention, the RF receiver of the badge is permanently on standby.It can also be provided that the badge is alternately on standby toreceive LF type signals and then RF type signals.

[0012] According to a modified embodiment, the process of communicationaccording to the invention can comprise the following steps:

[0013] emission of an LF type signal by a corresponding emitter of thevehicle,

[0014] reception of the LF type signal by a badge triggering the placingon standby of the RF receiver of the badge,

[0015] emission of an RF type signal by a corresponding emitter of thevehicle, this signal carrying a question posed to the badge for theidentification of this latter,

[0016] sending a response with an RF type signal of the badge toward thevehicle.

[0017] In this process, it can be provided that the LF type signalemitted by the vehicle contains information permitting identifying thevehicle. In this way, the badge is not placed in RF standby as soon asit receives an LF type signal but only when it receives an LF typesignal from the corresponding vehicle. The LF type signal is for exampleemitted by the vehicle according to a locking, unlocking or startingcommand.

[0018] During the phases of movement of the vehicle, checking of thevarious badges present in the vehicle can be carried out by emitting asignal of the RF type by a corresponding emitter of the vehicle, thissignal being the carrier of a question posed to the badge foridentification of this latter. The badge thus responds by the emissionof an RF type signal carrying a response to the received question.

[0019] The present invention also provides a process for managing thepresence of badges in a vehicle, according to which the vehicle emitswithin the vehicle an LF type signal and according to which in responseto this signal, each badge having detected the emitted LF type signal,emits in its turn an RF type signal, this signal comprising informationpermitting identifying the corresponding badge. According to theinvention, this process moreover comprises the following steps:

[0020] memorization of the list of badges having responded according toa location of the badge by sending an LF type signal,

[0021] emission of an RF type signal by a corresponding emitter of thevehicle, this signal being the bearer of a question posed to the badgefor identification of this latter,

[0022] sending a response with an LF type signal of the badge toward thevehicle,

[0023] comparison of the list of badges identified by the identificationof the RF/RF type with the list of memorized badges.

[0024] In this management process, a signal is preferably given to thedriver of the vehicle if it appears during the identification of theRF/RF type of the non-memorized badges. To avoid the detection of badgeslocated immediately adjacent the vehicle without being in the vehicle,this management process provides that the identification of the RF/RFtype badges is carried out only during movement of the vehicle.

[0025] The present invention also relates to an electronic badge adaptedto permit hands-free access to the motor vehicle, comprising a wavereceiver of the LF type and a wave emitter of the RF type, characterizedin that it also comprises a wave receiver of the RF type. Such a badgeis adapted to practice the communication processes described above.

[0026] The details and advantages of the present invention will becomebetter understood from the description which follows, with reference tothe accompanying schematic drawings, in which:

[0027]FIG. 1 shows schematically a motor vehicle seen from above,

[0028]FIG. 2 shows schematically a process for communication prior tounlocking the vehicle,

[0029]FIG. 3 shows schematically a process for communication formonitoring badges in the vehicle.

[0030] In FIG. 1, there is shown the different zones covered by the LF(Low Frequency) emitting antennas as well as by an RF (Radio Frequency)antenna associated with the vehicle 2.

[0031] There are two groups of LF antennas. A first group of antennascalled in what follows the exterior antennas, comprises four antennasdisposed in the external handles of the doors of the vehicle 2. Therange of each of these antennas is symbolized on the accompanyingdrawing a crosshatched circle 4. The second group of antennas, calledinterior antennas, comprises three antennas disposed in the passengerspace of the vehicle, for example on the floor of the passenger space.The range of each of these three antennas is symbolized in the drawingby a crosshatched oval 6.

[0032] Finally, the RF antenna is disposed in the passenger space of thevehicle 2 and has a range symbolized by a large circle 8 on the drawing.The range of emission of the RF antenna is of the order of tens ofmeters, for example about 30 meters, whilst the range of emission of theLF antennas is of the order of meters, for example 1 meter.

[0033] The signals emitted by the LF antennas, external and internal,have for example a frequency of 125 kHz, whilst the signals emitted bythe RF antenna have a frequency of 433 MHz.

[0034] All the indications given above as to the number of antennas, asto their position, as to their range or their frequency of emission, aregiven by way of example.

[0035] In FIG. 1, a first badge 10 has been shown by a square. Thisbadge is located outside the vehicle, for example in the pocket of adriver.

[0036] The process of communication between the first badge 10 and thevehicle is schematically shown in FIG. 2. At the bottom of this figure,there is symbolized the time axis T. A first line 12 shows schematicallya signal emitted by the external LF antennas. It will be seen that thefirst badge 10 is located in an emission zone 4 of an external antenna.

[0037] When the driver carrying the badge 10 wishes to open a door, amanagement device of the hands-free system of this vehicle commands theemission of an LF signal by the external antennas. This signal issymbolized by the curve 12.

[0038] In response to this signal, the badge 10 places its RF receiveron standby. This is symbolized by the curve 14 of FIG. 2. It can beprovided that the LF signal emitted by the external antennas contains achallenge. In this way, the RF receiver of the badge 10 goes on standbyonly if the LF signal received is a signal emitted by the correspondingvehicle. It can be a matter of a simple challenge comprising for exampleonly three octets of information.

[0039] The RF receiver of the badge 10 being on standby, it is ready toreceive the challenge thus emitted by the RF emitter of the vehicle 2.The curve 16 shows the signals emitted by this RF emitter. When thechallenge, also sometimes called code, is received by the badge, the RFreceiver of the badge 10 becomes inactive. The RF emitting portion ofthe badge 10 then goes on standby and responds to the management deviceof the hands-free system. If the response sent by the badge 10corresponds to the challenge emitted by the RF antenna of the vehicle,then the door of the vehicle will be unlocked.

[0040] A similar procedure could be used to start the vehicle. In thiscase, the LF signal is thus emitted by the internal antennas and nolonger by the external antennas, which remain silent.

[0041] Such procedures are based on the principle of doublecommunication by rising channel, which is to say from the vehicle towardthe badge, the LF one permitting locating the badge and the other RF onewhose role is to transmit the data of the challenge. The descendingchannel, which is to say from the badge toward the vehicle, RF sends theresponse to the management device of the system.

[0042]FIG. 3 shows schematically a process for communication between thevehicle 2 and a badge during a phase of movement of the vehicle. In thisFIG. 3, there will be seen as in FIG. 2, four curves each correspondingto an emitter or a receiver. Thus, the curve 22 corresponds to the LFemitters, the curve 24 to the RF receiver of the badge, the curve 26 tothe RF emitter of the vehicle and the curve 28 to the RF emitter of thebadge.

[0043] According to this procedure, during a moving phase of thevehicle, the LF antennas of the vehicle remain silent. The RF receiverof the badge remains itself on permanent standby. During this time, theRF emitting antenna of the vehicle emits challenges at regular timeintervals. These are challenges of a particular type which are sent onlyduring movement of the vehicle for locating the badges. Each badgepresent in the occupant space of the vehicle 2 thus responds to thesechallenges by emitting a response (curve 28).

[0044] The use of RF signals to communicate between the vehicle and thebadge permits communication with all of the badges present in theoccupant space of the vehicle.

[0045] In FIG. 1, a second badge 20 has been shown inside the occupantspace. This badge 20 is located in a region masked from LF reception. Ascan be seen in this figure, this badge 20 is not located in any of thezones 4 and 6 of emission of the external and internal LF antennas.Although located in the occupant space of the vehicle, the second badge20 cannot receive an LF signal emitted by the external and/or internalantennas. Thus, if the second badge 20 is forgotten within the vehicle2, the driver could lock and unlock his vehicle and start it with thehelp of his first badge 10. However, the driver does not know withcertainty that the second badge is located within the vehicle. If thissecond badge is visible from the outside, a person up to no good couldbreak in, take this badge, and start the vehicle as if he were theowner.

[0046] The communication process described with reference to FIG. 3permits avoiding this problem. Thus, as indicated above, all the badgespresent in the vehicle are detected because the emission range of the RFantenna, both of the vehicle antenna and that of the badge, covercompletely all the occupant space of the vehicle.

[0047] The invention thus also provides a process permitting signalingto the driver the presence of a badge located in a region masked from LFemission. An LF locating signal is thus emitted by the internal LFemitting antennas. The signal is received by all the badges located inthe zones 6 (FIG. 1) within the occupant space of the vehicle. Let it besupposed here that the badges are permanently on RF standby. A“conventional” signal of the RF type is thus emitted toward the badgesand these which have both received the LF signal and the RF signalrespond with an RF signal. The management device thus memorizes whichbadges send a response following the dispatch of the LF signal. Then,during a moving phase of the vehicle, the badges located within theinterior of the vehicle 2 are questioned by a particular locationrequest of the RF type. All the badges, even those located in a regionmasked from LF emission, then respond to this request. The managementdevice of the hands-free system of the vehicle then compares the list ofthe badges responding to the LF request, with the list of memorizedbadges. If these two lists differ, the management device then signals tothe driver that a badge is located in a region masked from LF emission.

[0048] The communication procedures described above thus permitdetecting all the badges present within the occupant space of thevehicle. Thus, during a process of locking the vehicle, the hands-freesystem must guarantee that there is no badge within the vehicle. Thus,if a badge remained in the vehicle, then by modification of the zones 4and 6 of LF emission, this badge would become visible to the external LFemitting antennas and would permit thus a third person to unlock thevehicle, recover the badge and also start the vehicle.

[0049] The communication processes described above permit solving theseproblems which arise in processes of communication of the prior artaccording to which the vehicle sends a challenge to the badge byemission of an LF signal and the badge responds to the vehicle byemission of an RF signal.

[0050] The present invention is not limited to the processes describedabove by way of non-limiting example but covers all modifications ofembodiment within the scope of persons skilled in the art, within thescope of the following claims.

1. Process for communication between a badge (10, 20) and a vehicle (2)according to which a short range emitter associated with the vehicleemits an LF type signal in the direction of the badge (10, 20) whichresponds by sending an RF type signal of longer range in the directionof the vehicle, characterized in that a receiver of the badge adapted toreceive an RF type signal is placed in standby according to apredetermined rhythm and in that an emitter associated with the vehiclesends, during a standby phase of the badge, an RF type signal to whichthe badge responds by an RF type signal.
 2. Communication processaccording to claim 1, characterized in that the RF receiver of the badgeis permanently on standby.
 3. Communication process according to claim1, characterized in that it comprises the following steps: emission ofan LF type signal (12) by a corresponding emitter of the vehicle,reception of the LF type signal by a badge triggering the standby of theRF signal (14) of the badge, emission of an RF type signal (16) by acorresponding emitter of the vehicle, this signal being the bearer of aquestion posed to the badge for identification of this latter, sending aresponse with an RF type signal (18) from the badge toward the vehicle.4. Communication process according to claim 3, characterized in that theLF type signal emitted by the vehicle contains information permittingidentifying the vehicle.
 5. Communication process according to one ofclaims 1 to 4, characterized in that the LF type signal is emitted bythe vehicle following a locking, unlocking or starting command. 6.Communication process according to claim 1, characterized in that duringthe moving phases of the vehicle, monitoring of the various badgespresent in the vehicle is carried out by emitting an RF type signal (26)by a corresponding emitter of the vehicle, this signal being the bearerof a question posed to the badge for identification of this latter, andin that the badge responds by emission of an RF type signal (28) bearinga response to the received question.
 7. Management process of thepresence of badges in a vehicle, according to which the vehicle emitswithin the vehicle an LF type signal and according to which in responseto this signal, each badge having detected the emitted LF type signal,emits in its turn an RF type signal, this signal comprising informationpermitting identifying the corresponding badge, characterized in that itcomprises moreover the following steps: memorization of the list ofbadges having responded to a badge location by sending an LF typesignal, emission of an RF type signal by a corresponding emitter of thevehicle, this signal being the bearer of a question posed to the badgefor identification of this latter, sending a response with an RF typesignal from the badge toward the vehicle, comparison of the list ofbadges identified by the RF/RF type identification, with the memorizedlist of badges.
 8. Management process according to claim 7,characterized in that a signal is given to the driver of the vehicle ifthere appear during the RF/RF type identification, un-memorized badges.9. Management process according to one of claims 7 or 8, characterizedin that the identification of the RF/RF type badges is carried out onlywhen the vehicle is in motion.
 10. Electronic badge (10, 20) adapted topermit a hands-free access to a motor vehicle, comprising a receiver ofLF type waves and an emitter of RF type waves, characterized in that italso comprises a receiver of RF type waves.